1st gear problem, 97 F-250, automatic

[DougC]

97 F-250, 7.3 liter, automatic: When I go down steep hills or driveways with the shifter locked in 1st gear, the truck acts like it's going in and out of gear. It will coast as if it were in neutral, then catch and give me 1st-gear compression braking, then coast again, and back and forth like that. It's acting like it's in 1st, then neutral, then 1st, then neutral, etc. The shifter is locked into low. I'm not going real fast and using the brakes to hold the truck back. Truck speed is maybe 5-20 mph. It doesn't act like any automatic I've ever driven in my life. One transmission tech tested it and agreed it's not supposed to do this coming down steep hills in 1st, but couldn't tell me what it would take to fix it. The tech said it shifts nicely when running through the gears under normal driving circumstances. The second transmission shop tech took a test ride with a tester plugged in under the dash that is supposed to analyze the tranny as the truck is driven. He said that this is how 1st gear is supposed to be, but 3rd and 4th are locking up at 80% instead of 100% and that I should let them rebuild the tranny for about $3750. He said I could even leave it there right then and they could get right on it. I need some help. Other than the 1st gear thing, the truck drives nicely and seems to shift fine to me and to the mechanic who checked it before I bought it about 500 miles ago. Any advice would be appreciated.

[Robby1]

I can't help with diagnostics. Just bought a 95 7.3 with auto and had/have some concerns with the tranny. Called Ford dealer and a rebuilt, installed, 3 year warrenty, done, finished, $2850.00. Includes torque converter. dealer is in Idaho.